The present invention relates generally to a method for the selective removal of near-surface regions of ceramic material from a ceramic body. More particularly, the present invention is directed to a method for the controlled removal of such near-surface regions to predetermined nanometer depths by implanting ions in a selected surface location of the ceramic body to damage and strain the lattice structure of the ceramic material in the near-surface regions of the ceramic body and then contacting these ion-damaged near-surface regions with collapsing, ultrasonically-generated cavitation bubbles for removing ceramic material therefrom to the predetermined depth.
This invention was made with the support of the United States Government under contract No. DE-AC05-840R21400 awarded by the U.S. Department of Energy. The United States Government has certain rights in this invention.
Ceramic materials of single-crystal or polycrystalline form are commonly used as substrates in the manufacture or packaging of various electronic and optical components and systems such as semi-conducting devices, integrated circuits, superconductors, ferroelectric conductors, optical modulating devices, optical wave guides, electrical sensors, gauges, and the like. The ceramic substrates or bodies used in such application are frequently of a complex or composite construction and are often doped with suitable materials so as to incorporate electrically conductive and/or semiconductive or electrical insulating phases at specific surface and subsurface regions in the ceramic substrate or body.
The utilization of ceramic materials in the manufacture of components and systems such as mentioned above, often requires that the surface of the ceramic substrate or body be altered or tailored by removing surface layers of thicknesses in the order of about 10-2000 nanometers and on a scale compatible with the processing or packaging required for the particular component or system. The removal of selected surface layers of electrically conductive or electrically insulating ceramic material from near-surface regions of ceramic bodies to desired depths such as for exposing a suitable electrical conducting or insulating surface has been previously achieved by employing techniques such as ultrasonic impact grinding with an abrasive such as boron carbide or the like or by using chemical etchants. Such impact grinding and chemical etching techniques have been found to have many drawbacks which detract from their use in removing selected surface layers of ceramic material from ceramic bodies. For example, with impact grinding techniques, the depth to which the surface layer is removed is often hard to control, especially in nanometer depths less than about 100 nanometers since the size of the abrasive particle is often of a particle size substantially greater than the desired depth of the surface layer to be removed from the ceramic article. Also, some of the abrasive particles are often imbedded in the ceramic surface so as to detract from the desired properties of the ceramic material. The use of presently known chemical etchants is often unsatisfactory for tailoring the surface of many ceramics due to particular properties and the nonuniform dissolution behavior of the ceramic materials. Chemical etchants subject the ceramic material to possible chemical reactions which could result in the removal or damage of heterogeneous adjacent material required by the electronic mechanism being fabricated from the ceramic material. Also, chemical etchants have been found to damage some ceramic material due to the relatively high temperatures generated during the chemical etching reaction.